Lyophilised peptides are stable because they are dry. Almost every storage rule follows from that one fact: keep water out, keep heat and light down, and open the vial as few times as possible. This guide covers the three states a research peptide passes through in a laboratory, sealed powder, opened powder and solution, and what changes at each step.
Why freeze-drying works
Lyophilisation removes water from a frozen solution by sublimation under vacuum. What is left is a porous, low-density cake or powder with very little residual moisture, typically a few percent measured by Karl Fischer titration. Without water, the two main degradation routes for peptides, hydrolysis of the peptide bond and deamidation of asparagine and glutamine residues, slow to a crawl. Oxidation of methionine, cysteine and tryptophan residues still happens but far more slowly than in solution.
This is why a sealed vial of lyophilised peptide can travel by post at ambient temperature for several days without meaningful loss, and why the same peptide in solution needs a fridge.
Sealed vials: before opening
Temperature. Store at -20°C for anything beyond a few weeks. At 2 to 8°C most lyophilised peptides remain within specification for months. Ambient temperature is acceptable for the days a vial spends in transit, which is how every supplier ships.
Light. Keep vials in their box. Tryptophan- and tyrosine-containing sequences are light-sensitive; amber glass helps but the box is simpler.
Moisture. The vial is sealed under a crimped cap, so the powder is protected until the seal is broken. Do not store opened boxes in a humid environment, and if a vial is taken from a freezer, let it reach room temperature before opening it so condensation does not form on the cold powder. This one step prevents more degradation than any other.
Shelf life. Suppliers usually state 24 months at -20°C for sealed lyophilised vials. Real stability depends on the sequence; short, simple peptides such as KPV or GHK-Cu are robust, while long sequences with several oxidisable residues, such as tesamorelin or TB-500, are more sensitive.
Opened vials: powder after the seal is broken
Once the cap is pierced, the vial is no longer sealed against moisture. If you are not reconstituting the whole vial, the remaining powder should be kept at -20°C in a desiccated container and used within a few weeks. In practice most laboratories reconstitute the whole vial and then aliquot the solution, which is easier to manage than weighing out fractions of a few milligrams of powder.
In solution
Reconstitution changes everything. Water is back, hydrolysis and deamidation resume, and microbial growth becomes possible.
Solvent. Bacteriostatic water, sterile water with 0.9% benzyl alcohol, is the standard laboratory solvent because the preservative allows the vial to be drawn from repeatedly. Sterile water without preservative is single-use. Some sequences with low solubility in water are first dissolved in a small volume of acetic acid or DMSO and then diluted; the certificate or the supplier can advise.
Temperature. Keep solutions at 2 to 8°C and use within 28 days, which is also the period the benzyl alcohol preservative is rated for. For longer holding, freeze aliquots at -20°C.
Freeze-thaw. Every freeze-thaw cycle stresses a peptide solution: ice crystals concentrate solutes and shift pH locally. Freeze once, in single-use aliquots, and thaw each one only when needed. Never refreeze a thawed aliquot.
Containers. Peptides adsorb to glass and some plastics, which matters at low concentrations. Low-binding polypropylene tubes are the usual choice for aliquots.
Working out concentration
Concentration is fill divided by volume: 10 mg reconstituted in 2 ml is 5 mg/ml. The Concentration Calculator on this site does the arithmetic, including the solvent volume needed for a target concentration. Record the concentration, the date and the lot number on every aliquot; a tube with no label is a tube you will throw away.
Signs of a problem
- Powder that has collapsed or looks glassy rather than a light cake usually means it has absorbed moisture.
- A solution that is cloudy or has visible particles after gentle swirling suggests aggregation or incomplete dissolution; do not shake vigorously, as foaming denatures peptides.
- Colour change in a normally white peptide indicates oxidation. GHK-Cu is blue by nature and is the exception.
Summary table
| State | Temperature | Light | Time |
|---|---|---|---|
| Sealed lyophilised | -20°C (2 to 8°C for months) | Boxed | Up to 24 months |
| In transit | Ambient | Boxed | Days |
| Opened powder | -20°C, desiccated | Boxed | Weeks |
| Solution, in use | 2 to 8°C | Dark | 28 days |
| Solution, aliquoted | -20°C, single freeze | Dark | Months |
Every BluePeak vial ships lyophilised with its lot number on the label, so the storage clock and the certificate both start from a known point.
Laboratory storage guidance only. BluePeak products are for research use and not for human or veterinary use.
